FileSenixGST Inclusive vs GST Exclusive Formula Explained
When calculating Goods and Services Tax (GST), you will encounter two different methods. The first method is called GST Exclusive, which means adding tax to a base price. The second method is called GST Inclusive, which means extracting tax from a total price that already includes tax.
Both methods use different formulas. Using the wrong formula can lead to incorrect calculations, which may cause problems on business invoices, tax returns, and financial reports.
This article explains both formulas step by step with clear examples so you can understand exactly how to add GST to a base price and how to extract GST from a total price.
Add or Extract GST Instantly
Use the free Filesenix GST Calculator to add or remove GST in one click.
GST Exclusive Formula: Adding Tax to a Base Price
The GST Exclusive formula is used when you know the base price of a product or service and you need to add GST on top of it. This is the most common calculation for businesses that need to create invoices.
Example: Adding 18% GST to a ₹1,000 Base Price
Let us say you have a product with a base price of ₹1,000 and the GST rate is 18%.
- Step 1: Calculate the GST amount. GST Amount = ₹1,000 × (18 ÷ 100) = ₹1,000 × 0.18 = ₹180.
- Step 2: Add the GST amount to the base price. Final Price = ₹1,000 + ₹180 = ₹1,180.
So the customer will pay ₹1,180 in total. The ₹1,000 is the base price and the ₹180 is the GST.
More Examples at Different GST Rates
5% GST on ₹2,000
GST = ₹2,000 × 0.05 = ₹100
Total = ₹2,100
12% GST on ₹5,000
GST = ₹5,000 × 0.12 = ₹600
Total = ₹5,600
28% GST on ₹10,000
GST = ₹10,000 × 0.28 = ₹2,800
Total = ₹12,800
GST Inclusive Formula: Extracting Tax from a Total Price
The GST Inclusive formula is used when you know the total price (which already includes GST) and you need to find out how much of that total is the base price and how much is the GST amount.
This formula is different from the exclusive formula. You cannot simply multiply the total price by the GST rate to find the GST amount. This is a common mistake that gives you the wrong answer.
Example: Extracting 18% GST from a ₹1,180 Total
Let us say you paid ₹1,180 for a product and the GST rate is 18%. You want to find out the base price and the GST amount.
- Step 1: Calculate the base price. Base Price = ₹1,180 ÷ (1 + 18 ÷ 100) = ₹1,180 ÷ 1.18 = ₹1,000.
- Step 2: Find the GST amount. GST Amount = ₹1,180 − ₹1,000 = ₹180.
So the base price of the product is ₹1,000 and the GST amount is ₹180.
The Common Tax Extraction Mistake
If a bill total is ₹1,180 including 18% GST, many people make the mistake of calculating 18% of ₹1,180 to find the GST amount.
Wrong calculation: ₹1,180 × 0.18 = ₹212.40 ❌
Correct calculation: ₹1,180 ÷ 1.18 = ₹1,000 (base price), then ₹1,180 − ₹1,000 = ₹180 (GST) ✅
The mistake happens because 18% GST was calculated on the base price (₹1,000), not on the final total (₹1,180). Always divide by (1 + rate) when extracting GST from a total.
Quick Reference: Division Factors for Common GST Rates
Here are the division factors you need to use when extracting GST from an inclusive price at different GST rates.
5% GST
÷ 1.05
12% GST
÷ 1.12
18% GST
÷ 1.18
28% GST
÷ 1.28
For example, to extract 12% GST from a total of ₹5,600, divide ₹5,600 by 1.12. The result is ₹5,000 (base price). The GST amount is ₹5,600 − ₹5,000 = ₹600.
When to Use Each Formula
Use the Exclusive Formula when you know the base price and need to calculate the total price including GST. This is common when creating business invoices.
Use the Inclusive Formula when you know the total price (with GST already included) and need to find the base price and GST amount separately. This is common when reading retail bills or MRP-tagged products.
Frequently Asked Questions
Why is multiplying an inclusive total by the GST rate incorrect?
Because GST was originally calculated on the smaller base price, not on the larger inclusive total. Multiplying the total by the GST rate gives a number that is too high. You must divide the total by (1 + GST rate) to get the correct base price first.
What is the formula to remove 18% GST from a total?
Divide the total amount by 1.18. For example, if the total is ₹1,180, the base price is ₹1,180 ÷ 1.18 = ₹1,000. The GST amount is ₹1,180 − ₹1,000 = ₹180.
How do I add 18% GST to a base price?
Multiply the base price by 0.18 to get the GST amount. Then add the GST amount to the base price. For example, for a base price of ₹1,000: GST = ₹1,000 × 0.18 = ₹180. Total = ₹1,000 + ₹180 = ₹1,180.
Does this formula work for all GST rates (5%, 12%, 18%, 28%)?
Yes! The same formula works for all GST rates. Just replace the GST rate in the formula with the correct rate. For 5%, divide by 1.05. For 12%, divide by 1.12. For 18%, divide by 1.18. For 28%, divide by 1.28.
Can I use these formulas for taxes other than GST?
Yes! These formulas work for any percentage-based tax, including VAT (Value Added Tax), sales tax, or service tax. Just replace the GST rate with the applicable tax rate.
Is the Filesenix GST Calculator free?
Yes! The Filesenix GST Calculator is 100% free to use. It handles both inclusive and exclusive calculations instantly with no sign-up required.